Herbicidal method using diflufenican

ABSTRACT

The invention provides a method of controlling the growth of weeds using (a) a urea herbicide and (b) diflufenican; herbicidal compositions comprising (a) and (b) are described.

The present invention relates to new herbicidal compositions comprising N-(2,4-difluorophenyl)-2-(3-trifluoromethylphenoxy)nicotinamide of the formula depicted in Figure I hereinafter, which is disclosed in the specification of British Patent Publication No. 2087887A as a pre- and/or post-emergence herbicide, and to their use in agriculture.

The extensive use of the urea herbicides and mixtures thereof by which certain weed species such as Galium aparine, Veronica hederifolia, Veronica persica and Viola arvensis are poorly controlled, has led to an increase in the population of Galium aparine, Veronica and Viola, such that they now constitute a serious weed problem in cereal growing.

As a result of research and experimentation it has been discovered that the use of the compound N-(2,4-difluorophenyl)-2-(3-trifluoromethylphenoxy)nicotinamide (hereinafter referred to for convenience as diflufenican) in combination with the urea herbicide extends its spectrum of activity to include the control of Galium aparine, Veronica spp., and Viola spp. Therefore the said combined use represents an important technological advance.

Surprisingly, in addition to this, it has been found that the combined herbicidal activity of diflufenican with the urea herbicide against certain weed species is much greater than expected when applied pre- or post-emergence (e.g. as a pre- or post-emergence spray), i.e. the herbicidal activity of diflufenican with the urea herbicide showed an unexpected and remarkable degree of synergism as defined by P. M. L. Tammes, Netherlands Journal of Plant Pathology, 70 (1964), pp. 73-80 in a paper entitled "Isoboles, a graphic representation of synergism in pesticides", or as defined by Limpel, L. E., P. H. Schuldt and D. Lamont, 1962, Proc. NEWCC 16:48-53, using the formula: ##EQU1## where E=the expected percent inhibition of growth by a mixture of two herbicides at defined doses.

X=the percent inhibition of growth by herbicide A at a defined dose

Y=the percent inhibition of growth by herbicide B at a defined dose

(when the observed response is greater than expected the combination is synergistic).

The remarkable synergism on Galium aparine and Avena fatua gives improved reliability of control of two of the most competitive weeds in cereal culture and leads to a considerable reduction in the amount of active ingredient required for weed control.

A high level of control of these species is desirable to prevent a) loss of yield, through competition or difficulties with harvesting and seed cleaning and b) to prevent unacceptable weed seed return to the soil.

It is to be understood that where in this specification reference is made to "the urea herbicide" it is intended to refer also to mixtures thereof where the context so permits. 2:1-1:2 wt/wt Mixtures, and more especially the 1:1 wt/wt mixtures, of isoproturon and neburon are preferred.

Accordingly the present invention provides a method for controlling the growth of weeds (i.e. undesired vegetation) at a locus which comprises applying to the locus amounts of (a) a urea herbicide, preferably a compound of the general formula:

    R.sup.1 N(R.sup.2)CON(R.sup.3)R.sup.4                      I

wherein R¹ represents an optionally substituted cyclic hydrocarbyl (which is preferably aromatic e.g. phenyl) or aromatic heterocyclyl (e.g. benzothiazol-2-yl) group, R² represents the hydrogen atom or a straight or branched chain alkyl group containing from 1 to 6 carbon atoms, R³ represents a straight or branched chain alkyl group containing from 1 to 6 carbon atoms or an optionally substituted cyclic hydrocarbyl (e.g. 2-methylcyclohexyl) group and R⁴ represents the hydrogen atom or a straight or branched chain alkyl or alkoxy group containing from 1 to 6 carbon atoms, and (b) diflufenican, which are herbicidally effective in combination. For this purpose, the urea herbicide and diflufenican are normally used in the form of herbicidal compositions (i.e. in association with compatible diluents or carriers and/or surface-active agents suitable for use in herbicidal compositions), for example as hereinafter described.

Preferred compounds of general formula I are those wherein R² represents the hydrogen atom or the methyl group and R³ represents the methyl group.

Compounds of general formula I wherein R¹ represents a phenyl group optionally substituted in the 3 and/or 4 positions relative to the nitrogen atom by a chlorine or bromine atom or by an optionally halogen-substituted straight- or branched-chain alkyl or alkoxy group containing from 1 to 6 carbon atoms or by a similarly optionally substituted phenoxy group or represents the benzothiazol-2-yl group are also preferred.

Especially preferred compounds of general formula I are those wherein R² represents the hydrogen atom, R³ represents the methyl group and

(a) R¹ represents a phenyl, 3-trifluoromethylphenyl or 4-chlorophenyl group and R⁴ represents the methyl group; or

(b) R¹ represents a 4-chlorophenyl group and R⁴ represents the methoxy group, which are known respectively as fenuron, fluometuron, monuron and monolinuron, and more especially compounds of general formula I wherein R² represents the hydrogen atom and R³ represents the methyl group and

(c) R¹ represents a 3-chloro-4-methylphenyl or 4-isopropylphenyl group and R⁴ represents the methyl group; or

(d) R¹ represents the 3,4-dichlorophenyl group and R⁴ represents a methyl, methoxy or butyl group; or

(e) R¹ represents the benzothiazol-2-yl group, R² represents the methyl group and R³ represents the methyl group and R⁴ represents the hydrogen atom, which are known respectively as chlortoluron, isoproturon, diuron, linuron, neburon and methabenzthiazuron.

The amounts of the urea herbicide and diflufenican applied vary with the nature of the weeds, the compositions used, the time of application, the climatic and edaphic conditions and (when used to control the growth of weeds in crop-growing areas) the nature of the crops. When applied to a crop-growing area, the rate of application should be sufficient to control the growth of weeds without causing substantial permanent damage to the crop. In general, taking these factors into account, application rates between 150 g and 10 kg of the urea herbicide and between 25 g and 750 g of diflufenican per hectare give good results. However, it is to be understood that higher or lower application rates may be used, depending upon the particular problem of weed control encountered.

The urea herbicide and diflufenican in combination may be used to control selectively the growth of weeds, for example to control the growth of those species hereinafter mentioned, by pre- or post-emergence application in a directional or non-directional fashion, e.g. by directional or non-directional spraying, to a locus of weed infestation which is an area used, or to be used, for growing crops, for example cereals, e.g. wheat, barley, oats, rye, maize and rice, soya beans, field and dwarf beans, peas, lucerne, cotton, peanuts, flax, onions, carrots, oilseed rape, sunflower, and permanent or sown grassland before or after sowing of the crop or before or after emergence of the crop. For the selective control of weeds at a locus of weed infestation which is an area used, or to be used, for the growing of crops, e.g. the crops hereinbefore mentioned, application rates between 150 g and 3500 g of the urea herbicide and between 25 g and 250 g of diflufenican per hectare are particularly suitable.

According to a feature of the present invention, there is provided a method for the control of the growth of weeds by pre- or post-emergence application which comprises the combined use of (a) a urea herbicide chosen from chlortoluron, isoproturon, linuron, methabenzthiazuron and neburon or mixtures, preferably 2:1-1:2 wt/wt mixtures, thereof, for example 2:1-1:2 wt/wt mixtures (and more especially the 1:1 wt/wt mixture) of isoproturon and neburon, and (b) diflufenican at application rates of between 500 and 3500 g/ha, preferably between 500 and 2500 g/ha, and between 50 and 250 g/ha respectively, of (a) and (b) in proportions of 70:1 to 2:1 and preferably 50:1 to 2:1 wt/wt of (a) to (b), to control a very wide spectrum of annual broad-leafed weeds and grass weeds in cereal crops, e.g. wheat, barley, oats and rye, without significant permanent damage to the crop. The combined use described above offers both foliar and residual activity and consequently can be employed over a long period of crop development, i.e. from pre-weed pre-crop emergence to post-weed post-crop emergence. In the method according to this feature of the present invention, application of the herbicides to control weeds in autumn-sown cereals is preferred.

In the method described above, the combined use of (a) a urea herbicide chosen from chlortoluron, isoproturon and neburon or 2:1-1:2 wt/wt mixtures thereof and (b) diflufenican in proportions of 20:1 to 4:1 wt/wt of (a) to (b) is preferred. The urea herbicide and diflufenican in combination may also be used to control the growth of weeds, especially those indicated below, by pre- or post-emergence application in established orchards and other tree-growing areas, for example forests, woods and parks, and plantations e.g. sugar cane, oil palm and rubber plantations. For this purpose they may be applied in a directional or non-directional fashion (e.g. by directional or non-directional spraying) to the weeds or to the soil in which they are expected to appear, before or after planting of the trees or plantations at application rates between 1000 g and 5000 g of the urea herbicide and between 100 g and 500 g of diflufenican per hectare.

The urea herbicide and diflufenican in combination may also be used to control the growth of weeds, especially those indicated below, at loci which are not crop-growing areas but in which the control of weeds is nevertheless desirable. Examples of such non-crop-growing areas include airfields, industrial sites, railways, roadside verges, the verges of rivers, irrigation and other waterways, scrublands and fallow or uncultivated land, in particular where it is desired to control the growth of weeds in order to reduce fire risks. When used for such purposes in which a total herbicidal effect is frequently desired, the active compounds are normally applied at dosage rates higher than those used in crop-growing areas as hereinbefore described. The precise dosage will depend upon the nature of the vegetation treated and the effect sought. Pre- or post-emergence application, and preferably pre-emergence application, in a directional or non-directional fashion (e.g. by directional or non-directional spraying) at application rates between 2500 g and 10 kg of the urea herbicide and between 200 g and 750 g of diflufenican per hectare are particularly suitable for this purpose.

By the term `pre-emergence application` is meant application to the soil in which the weed seeds or seedlings are present before emergence of the weeds above the surface of the soil. By the term `post-emergence application` is meant application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil. By the term `foliar activity` is meant herbicidal activity produced by application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil. By the term `residual activity` is meant herbicidal activity produced by application to the soil in which weed seeds or seedlings are present before emergence of the weeds above the surface of the soil, whereby seedlings present at the time of applicaton or which germinate subsequent to application from seeds present in the soil, are controlled.

Weeds that may be controlled by the method include:

    ______________________________________                                         Veronica persica   Spergula arvensis                                           Veronica hederifolia                                                                              Cerastium holosteoides                                      Stellaria media    Arenaria serpyllifolia                                      Lamium purpureum   Silene vulgaris                                             Lamium amplexicaule                                                                               Legousia hybrida                                            Aphanes arvensis   Geranium molle                                              Galium aparine     Geranium dissectum                                          Alopecurus myosuroides                                                                            Erysimum cheiranthoides                                     Matricaria inodora Descurainea sophia                                          Matricaria matricoides                                                                            Montia perfoliata                                           Anthemis arvensis  Anagallis arvensis                                          Anthemis cotula    Myosotis arvensis                                           Papaver rhoeas     Chenopodium album                                           Poa annua          Polygonum aviculare                                         Apera spica venti  Polygonum convolvulus                                       Phalaris paradoxa  Galeopsis tetrahit                                          Phalaris minor     Chrysanthemum segetum                                       Avena fatua                                                                    Lolium perenne                                                                 Lolium multiflorum                                                             Bromus sterilis                                                                Poa trivialis.                                                                 ______________________________________                                    

The pattern of persistence of the urea herbicide and the diflufenican allow the method of the present invention to be practised by the time-separated application of separate formulations.

In accordance with usual practice, a tank mix may be prepared prior to use by combining separate formulations of the individual herbicidal components.

The following Experiments illustrate the present invention:

EXPERIMENT 1

The following greenhouse experiment demonstrates the synergistic activity of the combined use of isoproturon and diflufenican in controlling the growth of certain weeds.

Greenhouse Experiment Showing Nature of Biological Synergism Between Isoproturon and Diflufenican

A factorial experiment with 25 treatments was carried out to investigate the interaction of isoproturon and diflufenican at a wide range of doses, i.e. 0, 125, 250, 500 and 1000 g a.i./ha of isoproturon plus diflufenican at 0, 125, 250, 500 and 1000 g a.i./ha as indicated in the matrix below.

    ______________________________________                                         Treatment                                                                             isoproturon g a.i./ha                                                   ______________________________________                                         diflufenican                                                                            (1)     (6)      (11)   (16)   (21)                                   g a.i./ha                                                                               0       125      250    500    1000                                            (2)     (7)      (12)   (17)   (22)                                            125     125 +    250 +  500 +  1000 +                                                  125      125    125    125                                             (3)     (8)      (13)   (18)   (23)                                            250     125 +    250 +  500 +  1000 +                                                  250      250    250    250                                             (4)     (9)      (14)   (19)   (24)                                            500     125 +    250 +  500 +  1000 +                                                  500      500    500    500                                             (5)     (10)     (15)   (20)   (25)                                            1000    125 +    250 +  500 +  1000 +                                                  1000     1000   1000   1000                                   ______________________________________                                    

All treatments were made in an appropriate volume of water by mixing appropriate quantities of a 50% w/v aqueous suspension concentrate of isoproturon (commercial product) and diflufenican formulated as an experimental wettable powder (Example 1 hereinafter) containing 50% w/w active ingredient to give the above dose rates/ha in a spray volume of 260 1/ha. All treatments were applied using a laboratory sprayer fitted with a Spraying Systems Teejet SS 8003E operating at 0.2.1 kgf/cm². Treatments were applied to 10-15 Galium aparine or Avena fatua seeds sown 1-2 cm deep in a loam soil in 9 cm diameter plastic

There were 3 replicate pots per treatment arranged in a randomised block design. The pots were watered by a combination of overhead and sub-irrigation after treatment. A visual assessment of weed control was made 21 days after treatment using a 0-10 scale where 0=no activity and 10=100% control compared to the untreated plants.

The mean % weed control was calculated for each species and tabulated below for each treatment of the 25 treatments hereinbefore indicated.

    ______________________________________                                         Galium            Avena                                                        ______________________________________                                         0    0      0      0    0       0    43   50   67   70                         47   80     87     90   93      50   70   83   90   93                         70   90     100    100  100     80   90   93   97   100                        80   100    100    100  100     90   97   97   100  100                        100  100    100    100  100     95   100  100  100  100                        ______________________________________                                    

From these results the 90% herbicidally effective dose (ED90) in g a.i./ha was calculated for diflufenican alone and isoproturon alone and diflufenican+125 g, 250 g, 500 g and 1000 g of isoproturon from the dose response curves.

    ______________________________________                                         Galium (ED90 g/ha)                                                                               Avena (ED90 g/ha)                                            ______________________________________                                         Diflufenican alone                                                                          484      Diflufenican alone                                                                            538                                       Diflufenican +                                                                              209      Diflufenican + 275                                       125 g/ha isoproturon  125 g/ha isoproturon                                     Diflufenican +                                                                              136      Diflufenican + 199                                       250 g/ha isoproturon  250 g/ha isoproturon                                     Diflufenican +                                                                              125      Diflufenican + 122                                       500 g/ha isoproturon  500 g/ha isoproturon                                     Diflufenican +                                                                              106      Diflufenican + 107                                       1000 g/ha isoproturon 1000 g/ha isoproturon                                    Isoproturon alone                                                                           (no      Isoproturon alone                                                                             5668                                                   activity)                                                         ______________________________________                                    

The values given above were then used to plot ED90 isoboles for a) a "one sided effect" (Tammes p. 74 FIG. 1) in the case of Galium which was resistant to isoproturon, which is depicted in Figure (i) hereinafter

and b) a "two sided effect" (Tammes p. 75 FIG. 2) in the case of Avena where both compounds were active, which is depicted in Figure (ii) hereinafter

Figures (i) and (ii) clearly demonstrate type II and III isoboles respectively, which are characteristic of synergism.

ED90s were used for the construction of isoboles as 90% represents the desired level of weed control in an agricultural situation (see isobole for amitrole/atrazine synergism, Tammes FIG. 5 p. 77).

EXPERIMENT 2

A similar experiment to that hereinbefore described in Experiment 1 was carried out with chlortoluron and diflufenican against Avena fatua and gave the following results:

    ______________________________________                                                               ED 90 (g/ha)                                             ______________________________________                                         Diflufenican alone      586    g/ha                                            Diflufenican + 125 g/ha chlortoluron                                                                   450    g/ha                                            Diflufenican + 250 g/ha chlortoluron                                                                   300    g/ha                                            Diflufenican + 500 g/ha chlortoluron                                                                   95     g/ha                                            Diflufenican + 1000 g/ha chlortoluron                                                                  75     g/ha                                            Chlortoluron alone      2186   g/ha                                            ______________________________________                                    

These results, plotted in Figure (iii) hereinafter, for a "two sided effect" (Tammes p. 75 FIG. 2) clearly demonstrate a type III isobole characteristic of synergism.

EXPERIMENT 3 Greenhouse Experiment Showing Nature of Biological Synergism Between Neburon and Diflufenican

A factorial experiment with 43 treatments was carried out to investigate the interaction of neburon and diflufenican at a wide range of doses, i.e. 0, 125, 250, 500, 1000, 2000 and 4000 g a.i./ha of neburon plus diflufenican at 0, 31.25, 62.5, 125, 250, 500 and 1000 g a.i./ha as indicated in the matrix below.

    __________________________________________________________________________     Treatments:                                                                           neburon g a.i./ha                                                       __________________________________________________________________________     Diflufenican                                                                          (1) (2) (3)  (4) (5)  (6) (7)                                           g a.i./ha                                                                             0   125 250  500 1000 2000                                                                               4000                                                 (8) (9) (10) (11)                                                                               (12) (13)                                                                               --                                                   31.25                                                                              125 +                                                                              250 +                                                                               500 +                                                                              1000 +                                                                              2000 +                                                       31.25                                                                              31.25                                                                               31.25                                                                              31.25                                                                               31.25                                                    (14)                                                                               (15)                                                                               (16) (17)                                                                               (18) (19)                                                                               --                                                   62.5                                                                               125 +                                                                              250 +                                                                               500 +                                                                              1000 +                                                                              2000 +                                                       62.5                                                                               62.5 62.5                                                                               62.5 62.5                                                     (20)                                                                               (21)                                                                               (22) (23)                                                                               (24) (25)                                                                               --                                                   125 125 +                                                                              250 +                                                                               500 +                                                                              1000 +                                                                              2000 +                                                       125 125  125 125  125                                                      (26)                                                                               (27)                                                                               (28) (29)                                                                               (30) (31)                                                                               --                                                   250 125 +                                                                              250 +                                                                               500 +                                                                              1000 +                                                                              2000 +                                                       250 250  250 250  250                                                      (32)                                                                               (33)                                                                               (34) (35)                                                                               (36) (37)                                                                               --                                                   500 125 +                                                                              250 +                                                                               500 +                                                                              1000 +                                                                              2000 +                                                       500 500  500 500  500                                                      (38)                                                                               (39)                                                                               (40) (41)                                                                               (42) (43)                                                                               --                                                   1000                                                                               125 +                                                                              250 +                                                                               500 +                                                                              1000 +                                                                              2000 +                                                       1000                                                                               1000 1000                                                                               1000 1000                                              __________________________________________________________________________

All treatments were made in an appropriate volume of water to give the above dose rates/hectare in a spray volume of 290 1/ha. The neburon was formulated as an experimental 25% w/w wettable powder (Example 9 hereinafter). The diflufenican was an experimental aqueous suspension concentrate (Example 2 hereinafter) containing 50% w/v active ingredient. All treatments were applied using a laboratory sprayer fitted with a Spraying Systems Teejet SS 8003E operating at 2.95 kgf/cm².

Treatments were applied post-emergence to Galium aparine at the 2 whorls growth stage. Plants were grown in non-sterile clay loam in 7 cm square plastic pots. There were four replicated pots per treatment and these were arranged in randomised blocks in the glasshouse. The pots were watered by a combination of overhead and sub-irrigation after treatment.

A visual assessment of weed control on a 0-100 scale was made 22 days after treatment. The mean % weed control was calculated for each treatment for each species. From these results the 90% herbicidally effective dose (ED 90) in g ai/ha was calculated for diflufenican alone, neburon alone and for diflufenican +125, 250, 500, 1000 and 2000 g a.i./ha neburon from the dose response curves for Galium aparine.

    ______________________________________                                         Galium (ED90 g/ha)                                                             ______________________________________                                         Diflufenican alone    459                                                      Diflufenican + 125 g/ha neburon                                                                      218                                                      Diflufenican + 250 g/ha neburon                                                                      127                                                      Diflufenican + 500 g/ha neburon                                                                       49                                                      Diflufenican + 1000 g/ha neburon                                                                      22                                                      Diflufenican + 2000 g/ha neburon                                                                      15                                                      Neburon alone         5185                                                     ______________________________________                                    

The ED90 values were used to plot a "two sided effect" isobole for Galium given in Figure (iv) hereinafter. The isobole was of type III clearly demonstrative of synergism (Tammes, p. 75 FIG. 2).

EXPERIMENT 4 Greenhouse Experiment Showing the Nature of Biological Synergism Between Linuron and Diflufenican

A similar experiment to that hereinbefore described in Experiment 3 was carried out with linuron and diflufenican using 0, 250, 500, 1000 and 2000 g a.i./ha of linuron formulated as a 50% w/w wettable powder (commercial product) plus diflufenican at 31, 125, 500 and 1000 g a.i./ha. The following ED₉₀ values were computed from the results.

    ______________________________________                                                            ED90 g/ha                                                   ______________________________________                                         Diflufenican alone   684                                                       Diflufenican + linuron 250 g/ha                                                                     201                                                       Diflufenican + linuron 500 g/ha                                                                      69                                                       Diflufenican + linuron 1000 g/ha                                                                    less than 31                                              Diflufenican + linuron 2000 g/ha                                                                    less than 31                                              ______________________________________                                    

The results, plotted in Figure (v) hereinafter for a "two sided effect" (Tammes, p 75, FIG. 2) clearly demonstrate a type III isobole characteristic of synergism.

EXPERIMENT 5 Greenhouse Experiment Showing the Nature of Biological Synergism Between Diuron and Diflufenican

A similar experiment to that hereinbefore described in Experiment 3 was carried out with diuron and diflufenican using 0 and 187.5 g a.i./ha of diuron formulated as an 80% w/w wettable powder (commercial product) plus diflufenican at 31, 63, 125, 250, 500 g a.i./ha.

The observed weed control results are compared with the expected result using the Limpel formula: ##EQU2##

    ______________________________________                                                           Diuron g/ha                                                                    187.5                                                                  % control                                                                              0     Observed Expected (E)                                  ______________________________________                                         Diflufenican g/ha                                                                          0         --     60    --                                                      31        43     93    78                                                      63        68    100    87                                                      125       73    100    89                                                      250       83    100    93                                                      500       85     99    94                                          ______________________________________                                    

As the observed responses with the mixtures were higher than the expected figures the combinations were clearly synergistic.

EXPERIMENT 6

The efficacy of these synergistic mixtures for broad spectrum weed control in cereals was demonstrated in a series of small plot field trials where mixtures of diflufenican (Example 2 hereinafter) and isoproturon were compared to isoproturon alone.

The treatments were applied pre- or post-emergence to three replicate 6 m×3 m randomised plots at a total of 21 field sites in a volume of 141 liters/ha using a motorised small plot spraying machine fitted with 6×80015 Spraying Systems Teejets. Mixtures were achieved by spraying the plots with each component separately within minutes of each other (i.e. total volume of 282 1/ha).

Weed control was assessed after 3 months by counting the number of weeds in 2×0.5 m² quadrats per plot. Crops were assessed for any visual phytotoxicity on a scale of 0-100, where 0=no damage and 100=100% kill.

The results are shown in Table I below.

                                      TABLE I                                      __________________________________________________________________________              mean percentage control of weed numbers                                                                         *                                    Treatment                                                                               Am Pa Ga Vp Vh Va Lp Sm Mi Pr Aa Ba                                                                               Whe                                __________________________________________________________________________     Isoproturon                                                                           (a)                                                                               93.sup.(3)                                                                        84.sup.(5)                                                                       31.sup.(4)                                                                         24.sup.(6)                                                                        13.sup.(1)                                                                       26.sup.(5)                                                                         31.sup.(2)                                                                        83.sup.(6)                                                                        99.sup.(3)                                                                       100.sup.(1)                                                                       100.sup.(1)                                                                       2.sup.(4)                                                                        1.sup.(6)                          2000 g/ha                                                                             (b)                                                                               88.sup.(4)                                                                       --  0.sup.(2)                                                                         60.sup.(4)                                                                       -- -- -- 100.sup.(2)                                                                       100.sup.(2)                                                                       -- -- 2.sup.(4)                                                                        1.sup.(2)                          Isoproturon                                                                           (a)                                                                              100.sup.(3)                                                                        99.sup.(5)                                                                       83.sup.(4)                                                                        100.sup.(6)                                                                       100.sup.(1)                                                                       98.sup.(5)                                                                        100.sup.(2)                                                                       100.sup.(6)                                                                       100.sup.(3)                                                                       100.sup.(1)                                                                       100.sup.(1)                                                                       4.sup.(5)                                                                        2.sup.(6)                          1500 g/ha +                                                                    diflufenican                                                                          (b)                                                                               93.sup.(3)                                                                       -- 86.sup.(2)                                                                        100.sup.(4)                                                                       -- -- -- 100.sup.(2)                                                                       100.sup.(2)                                                                       -- -- 3.sup.(4)                                                                        1.sup.(2)                          125 g/ha                                                                       Isoproturon                                                                           (a)                                                                              100.sup.(3)                                                                       100.sup.(5)                                                                       99.sup.(4)                                                                        100.sup.(6)                                                                       100.sup. (1)                                                                      95.sup.(5)                                                                         99.sup.(2)                                                                       100.sup.(6)                                                                       100.sup.(3)                                                                       100.sup.(1)                                                                       100.sup.(1)                                                                       8.sup.(4)                                                                        5.sup.(6)                          1500 g/ha +                                                                    diflufenican                                                                          (b)                                                                               93.sup.(3)                                                                       -- 99.sup.(4)                                                                        100.sup.(4)                                                                       -- -- -- 100.sup.(2)                                                                       100.sup.(2)                                                                       -- -- 4.sup.(4)                                                                        2.sup.(2)                          250 g/ha                                                                       __________________________________________________________________________      Suffix in parenthesis = no. of occurrences                                     Am = Alopecurus myosuroides                                                    Pa = Poa annua                                                                 Ga = Galium aparine                                                            Vp = Veronica persica                                                          Vh = Veronica hederifolia                                                      Va = Viola arvensis                                                            Lp = Lamium purpureum                                                          Sm = Stellaria media                                                           Mi = Matricaria inodora                                                        Pr = Papaver rhoeas                                                            Aa = Aphanes arvensis                                                          (a) = Preemergence                                                             (b) = Postemergence                                                             *mean % crop phytotoxicity (highest recorded) Ba = barley Wh = wheat    

EXPERIMENT 7

The efficacy of these synergistic mixtures for broad spectrum weed control in cereals was demonstrated in a series of small plot field trials where tank mixtures of diflufenican (Example 2 hereinafter) and chlortoluron were compared with diflufenican alone.

The treatments were applied pre-emergence to three replicate 6 m×3 m randomised plots at six field sites in a volume of 261 1/ha using a motorised small plot spraying machine fitted with 6×8004 Spraying Systems Tee Jets.

Weed control was assessed in the spring following autumn application by counting the number of weeds in 3×0.5 m² quadrats per plot. Crops were assessed for any visual phytotoxicity on a scale of 0-100 where 0=no damage and 100=100% kill.

The results are shown in Table II below.

                                      TABLE II                                     __________________________________________________________________________                                          *                                                mean percentage control of weed numbers                                                                      Winter                                    Treatment                                                                             An.a                                                                              Aa As Cs La Pr Rr Sm Mi Vp Wh Ba Rye                                 __________________________________________________________________________     Chlortoluron                                                                          100.sup.(1)                                                                       100.sup.(1)                                                                       100.sup.(1)                                                                       99.sup.(1)                                                                        99.sup.(1)                                                                        99.sup.(2)                                                                         99.sup.(1)                                                                       99.sup.(3)                                                                        99.sup.(2)                                                                        99.sup.(1)                                                                        0.sup.(1)                                                                         5.7.sup.(4)                                                                       0.sup.(1)                           1500 g/ha +                                                                    diflufenican                                                                   62.5 g/ha                                                                      Diflufenican                                                                          100.sup.(1)                                                                       100.sup.(1)                                                                       100.sup.(1)                                                                        0.sup.(1)                                                                        99.sup.(1)                                                                        72.sup.(2)                                                                        100.sup.(1)                                                                       99.sup.(3)                                                                        99.sup.(2)                                                                        99.sup.(1)                                                                        0.sup.(1)                                                                         3.7.sup.(4)                                                                       0.sup.(1)                           125 g/ha                                                                       __________________________________________________________________________      Suffix in parenthesis = number of occurrences.                                 An.a = Anagallis arvensis                                                      As = Arenaria serpyllifolia                                                    Cs = Chrysanthemum segetum                                                     La = Lamium amplexicaule                                                       Rr = Raphanus raphanistrum                                                     * mean % crop phytotoxicity (highest recorded).                          

EXPERIMENT 8

Field trials were carried out in Belgium with tank-mixtures of diflufenican (Example 2 hereinafter) with isoproturon:neburon (1:1) or methabenzthiazuron. The treatments were applied in the autumn pre-emergence to replicate 30 m² plots to control a range of broad leaf and grass weeds in winter wheat and winter barley in a volume of 500 1/ha using a hand held sprayer. Assessments of weed control were made in the spring following autumn application. Crop phytotoxicity was recorded during the winter and spring and the maximum recorded damage is given with the results shown in Table III below.

                                      TABLE III                                    __________________________________________________________________________                                        Max. recorded                                                                  phytotoxicity                                                                  on wheat or                                                 mean % phytotoxicity                                                                              barley                                                      Am Pa Mi Sm Ga V spp                                                                              Wheat/Barley                                __________________________________________________________________________     Diflufenican +                                                                           125 g/ha +                                                                           95.sup.(3)                                                                        100.sup.(1)                                                                       100.sup.(2)                                                                       100.sup.(3)                                                                       100.sup.(1)                                                                       100.sup.(1)                                                                         8.sup.(4)                                  neburon + 800 g/ha +                                                           isoproturon                                                                              800 g/ha                                                             Diflufenican +                                                                           200 g/ha +                                                                           93.sup.(4)                                                                         99.sup.(1)                                                                       100.sup.(3)                                                                       100.sup.(4)                                                                        97.sup.(2)                                                                       100.sup.(1)                                                                        10.sup.(4)                                  methabenzthiazuron                                                                       1750 g/ha                                                            __________________________________________________________________________      Suffix in parenthesis = no. of occurrences                                     V spp =  Veronica spp                                                    

These trials demonstrate clearly the wide spectrum control including Galium aparine, Veronica and of Viola which can be obtained with the mixtures.

According to a further feature of the present invention, there are provided compositions suitable for herbicidal use comprising (a) the urea herbicide and (b) diflufenican in proportions of preferably 400:1 to 1:5 wt/wt of (a) to (b) [preferably 70:1 to 2:1 wt/wt of (a) to (b) and more preferably 20:1 to 4:1 wt/wt of (a) to (b)] in association with, and preferably homogeneously dispersed in, one or more compatible herbicidally-acceptable diluents or carriers and/or surface-active agents (i.e. diluents or carriers or surface-active agents of the type generally accepted in the art as being suitable for use in herbicidal compositions and which are compatible with the urea herbicide and diflufenican). The term "homogeneously dispersed" is used to include compositions in which the urea herbicide and diflufenican are dissolved in the other components. The term "herbicidal compositions" is used in a broad sense to include not only compositions which are ready for use as herbicides but also concentrates which must be diluted before use. Preferably, the compositions contain from 0.05 to 90% by weight of the urea herbicide and diflufenican.

The herbicidal compositions may contain both a diluent or carrier and a surface-active (e.g. wetting, dispersing, or emulsifying) agent. Surface-active agents which may be present in herbicidal compositions of the present invention may be of the ionic or non-ionic types, for example sulphoricinoleates, quaternary ammonium derivatives, products based on condensates of ethylene oxide with nonyl- or octyl-phenols, or carboxylic acid esters of anhydrosorbitols which have been rendered soluble by etherification of the free hydroxy groups by condensation with ethylene oxide, alkali and alkaline earth metal salts or sulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodium sulphono-succinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates. Examples of suitable solid diluents or carriers are aluminium silicate, talc, calcined magnesia, kieselguhr, tricalcium phosphate, powdered cork, adsorbent carbon black and clays such as kaolin and bentonite. The solid compositions (which may take the form of dusts, granules or wettable powders) are preferably prepared by grinding the urea herbicide and diflufenican with solid diluents or by impregnating the solid diluents or carriers with solutions of the urea herbicide and diflufenican in volatile solvents, evaporating the solvents and, if necessary, grinding the products so as to obtain powders. Granular formulations may be prepared by absorbing the urea herbicide and diflufenican (dissolved in volatile solvents) onto the solid diluents or carriers in granular form and evaporating the solvents, or by granulating compositions in powder form obtained as described above. Solid herbicidal compositions, particularly wettable powders, may contain wetting or dispersing agents (for example of the types described above), which may also, when solid, serve as diluents or carriers.

Liquid compositions according to the invention may take the form of aqueous, organic or aqueous-organic solutions, suspensions and emulsions which may incorporate a surface-active agent. Suitable liquid diluents for incorporation in the liquid compositions include water, acetophenone, cyclohexanone, isophorone, toluene, xylene and mineral, animal and vegetable oils (and mixtures of these diluents). Surface-active agents, which may be present in the liquid compositions, may be ionic or non-ionic (for example of the types described above) and may, when liquid, also serve as diluents or carriers.

Wettable powders and liquid compositions in the form of concentrates may be diluted with water or other suitable diluents, for example mineral or vegetable oils, particularly in the case of liquid concentrates in which the diluent or carrier is an oil, to give compositions ready for use. When desired, liquid compositions of the urea herbicide and diflufenican may be used in the form of self-emulsifying concentrates containing the active substances dissolved in the emulsifying agents or in solvents containing emulsifying agents compatible with the active substances, the simple addition of water to such concentrates producing compositions ready for use.

Liquid concentrates in which the diluent or carrier is an oil may be used without further dilution using the electrostatic spray technique.

Herbicidal compositions according to the present invention may also contain, if desired, conventional adjuvants such as adhesives, protective colloids, thickeners, penetrating agents, stabilisers, sequestering agents, anti-caking agents, colouring agents and corrosion inhibitors. These adjuvants may also serve as carriers or diluents.

Preferred herbicidal compositions according to the present invention are aqueous suspension concentrates which comprise from 10 to 70% w/v of the urea herbicide and diflufenican, from 2 to 10% w/v of. surface-active agent, from 0.1 to 5% w/v of thickener and from 15 to 87.9% by volume of water; wettable powders which comprise from 10 to 90% w/w of the urea herbicide and diflufenican, from 2 to 10% w/w of surface-active agent and from 10 to 88% w/w of solid diluent or carrier; liquid water soluble concentrates which comprise from 10 to 30% w/v of the urea herbicide and diflufenican, from 5 to 25% w/v of surface-active agent and from 45 to 85% by volume of water-miscible solvent, e.g. dimethylformamide; liquid emulsifiable suspension concentrates which comprise 10 to 70% w/v of the urea herbicide and diflufenican, from 5 to 15% w/v of surface-active agent, from 0.1 to 5% w/v of thickener and from 10 to 84.9 % by volume of organic solvent; granules which comprise from 2 to 10% w/w of the urea herbicide and diflufenican, from 0.5 to 2% w/w of surface-active agent and from 88 to 97.5% w/w of granular carrier and emulsifiable concentrates which comprise from 0.05 to 90% w/v, and preferably from 1 to 60% w/v, of the urea herbicide and diflufenican, from 0.01 to 10% w/v, and preferably from 1 to 10% w/v, of surface-active agent and from 9.99 to 99.94%, and preferably from 39 to 98.99%, by volume of organic solvent.

Herbicidal compositions according to the present invention may also comprise the urea herbicide and diflufenican in association with, and preferably homogeneously dispersed in, one or more other pesticidally active compounds and, if desired, one or more compatible pesticidally acceptable diluents or carriers, surface-active agents and conventional adjuvants as hereinbefore described. Examples of other pesticidally active compounds which may be included in, or used in conjunction with, the herbicidal compositions of the present invention include herbicides, for example to increase the range of weed species controlled, for example alachlor [α-chloro-2,6-diethyl-N-(methoxymethyl)acetanilide], asulam [methyl (4-aminobenzenesulphonyl)carbamate], alloxydim Na [sodium salt of 2-(1-allyloxyaminobutylidine)-5,5-dimethyl-4-methoxycarbonylcyclohexane-1,3-dione], atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-prop-ethyl [ethyl N-benzoyl-N-(3,4-dichlorophenyl-2-aminopropionate], bromoxynil [3,5-dibromo-4-hydroxy-benzonitrile](preferred), butachlor [N-(butoxymethyl)-α-chloro-2,6-diethylacetanilide], butylate [S-ethyl N,N-diisobutyl(thiocarbamate)], carbetamide [D-N-ethyl-2-(phenyl carbamoyloxy)propionamide], chlorfenpropmethyl [methyl 2-chloro-2-(4-chlorophenyl)propionate], chlorpropham [isopropyl N-(3-chlorophenyl)carbamate], cyanazine [2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine], cycloate [N'-cyclohexyl-N- ethyl-S-ethyl(thiocarbamate)], 2,4-D [2,4-dichlorophenoxyacetic acid], dalapon [2,2-dichloropropionic acid], 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid], desmedipham [3-(ethoxycarbonylamino)phenyl N-phenylcarbamate], diallate [S-2,3-dichloroallyl-N,N-diisopropyl(thiocarbamate)], dicamba [3,6-dichloro-2-methoxybenzoic acid], dichlorprop [(±)-2-(2,4dichlorophenoxy)propionic acid], difenzoquat [1,2-dimethyl-3,5-diphenyl-pyrazolium salts], dinitramine [N¹,N¹ -diethyl-2,6-dinitro-4-trifluoromethyl-m-phenylenediamine], EPTC [S-ethyl N,N-dipropyl(thiocarbamate), ethofumesate [2-ethoxy-2,3-dihydro-3,3-dimethyl-benzofuran-5-yl methylsulphonate], flamprop-isopropyl [isopropyl (±)-2-(N-benzoyl-3-chloro-4-fluoroanilino)propionate], flamprop-methyl [methyl (±)- 2-(N-benzoyl-3-chloro-4-fluoroanilino)-propionate], ioxynil [4-hydroxy-3,5-di-iodobenzonitrile](preferred), MCPA [4-chloro-2-methyl-phenoxyacetic acid], MCPB [4-(4-chloro-2-methylphenoxy)butyric acid], mecoprop [(±)-2-(4-chloro-2-methyl-phenoxy)propionic acid](preferred), metamitron [4-amino-3-methyl-6-phenyl-1,2,4-triazin-5-(4H)-one],metribuzin [4-amino-6-t-butyl-3-(methylthio)-1,2,4-triazin-5(4H)-one], molinate [S-ethyl N,N-hexamethylene(thiocarbamate)], oxadiazon [3-(2,4-dichloro-5-isopropoxyphenyl)-5-t-butyl-1,3,4-oxadiazolin-2-one], paraquat [1,1'-dimethyl-4,4'-(thiocarbamate)], phenmedipham [3-(methoxy-carbonylamino)phenyl N-(3-methylphenyl)carbamate], prometryne [4,6-bisisopropylamino-2-methylthio-1,3,5-triazine], propachlor [α-chloro-N-isopropyl-acetanilide], propanil [N-(3,4-dichlorophenyl)propionamide]propham [isopropyl N-phenylcarbamate], pyrazone [5-amino-4-chloro-2-phenylpyridazin-3(2H)-one], bypridylium salts], pebulate [s-propyl n-butyl-n-ethyl simazine [2-chloro-4,6-bisethylamino-1,3,5triazine], TCA (trichloroacetic acid), thiobencarb [S-(4-chlorobenzyl)-N,N-diethylthiolcarbamate], triallate [S-2,3,3-trichloroallyl N,N-di-isopropyl(thiocarbamate)], and trifluralin [2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline]; insecticides, e.g. carbaryl [naphth-1-yl N-methylcarbamate]; synthetic pyrethroids, e.g. permethrin and cypermethrin; and fungicides, e.g. 2,6-dimethyl-4-tridecyl-morpholine, methyl N-(1-butylcarbamoyl-benzimidazol-2-yl)carbamate, 1,2-bis-(3-methoxy-carbonyl-2-thioureido)benzene, isopropyl 1-carbamoyl-3-(3,5-dichlorophenyl)hydantoin and 1-(4-chloro-phenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)-butan-2-one. Other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention are plant growth regulators, e.g. succinamic acid, (2-chloroethyl)trimethylammonium chloride and 2-chloroethane-phosphonic acid; or fertilizers, e.g. containing nitrogen, potassium and phosphorus and trace elements known to be essential to successful plant life, e.g. iron, magnesium, zinc, manganese, cobalt and copper.

Pesticidally active compounds and other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention, for example those hereinbefore mentioned, and which are acids, may, if desired, be utilized in the form of conventional derivatives, for example alkali metal and amine salts and esters.

The compositions of the invention may be made up as an article of manufacture comprising the urea herbicide and diflufenican and optionally other pesticidally active compounds as hereinbefore described or, as is preferred, a herbicidal composition as hereinbefore described, and preferably a herbicidal concentrate which must be diluted before use, comprising the urea herbicide and diflufenican within a container for the aforesaid urea herbicide and diflufenican or a said herbicidal composition, and instructions physically associated with the aforesaid container setting out the manner in which the aforesaid urea herbicide and diflufenican or herbicidal composition contained therein is to be used to control the growth of weeds. The containers will normally be of the types conventionally used for the storage of chemical substances which are solids at normal ambient temperatures and herbicidal compositions, particularly in the form of concentrates, for example cans and drums of metal, which may be internally-lacquered, and plastics materials, bottles of glass and plastics materials and, when the contents of the container is a solid, for example granular herbicidal compositions, boxes, for example of cardboard, plastics materials and metal, or sacks. The containers will normally be of sufficient capacity to contain amounts of the active ingredients or herbicidal compositions sufficient to treat at least one acre of ground to control the growth of weeds therein but will not exceed a size which is convenient for conventional methods of handling. The instructions will be physically associated with the container, for example by being printed directly thereon or on a label or tag affixed thereto. The directions will normally indicate that the contents of the container, after dilution if necessary, are to be applied to control the growth of weeds at rates of application between 150 g and 10 kg of the urea herbicide and between 25 g and 750 g of diflufenican per hectare in the manner and for the purposes hereinbefore described.

According to a further feature of the present invention, there is provided a product comprising (a) a urea herbicide and (b) diflufenican as a combined preparation for simultaneous, separate or sequential use in controlling the growth of weeds at a locus.

The following examples illustrate herbicidal compositions according to the present invention and herbicidal compositions suitable for use in the method for controlling the growth of weeds according to the present invention.

EXAMPLE 1

A wettable powder was formed thus:

    ______________________________________                                         Diflufenican            50% w/w                                                Nekal BX (sodium alkyl naphthalene                                                                     10% w/w                                                sulphonate)                                                                    Sodium lignosulphonate  3% w/w                                                 Sopropon T36 (sodium polycarboxylate)                                                                  0.5% w/w                                               Hymod AT (ball clay)    to 100% w/w                                            ______________________________________                                    

EXAMPLE 2

An aqueous suspension concentrate was formed from:

    ______________________________________                                         Diflufenican             50% w/v                                               Ethylan BCP (a nonylphenol-ethylene                                                                     0.5% w/v                                              oxide condensate containing 9 moles                                            of ethylene oxide per mole of phenol)                                          Soprophor FL (triethanolamine salt of                                                                   1.0% w/v                                              oxyethylated polyarylphenolphosphate)                                          Sopropon T36 (sodium polycarboxylate)                                                                   0.5% w/v                                              Antifoam FD              0.1% w/v                                              Rhodigel 23 (xanthan gum)                                                                               0.2% w/v                                              Dichlorophen sodium solution, 40% w/w                                                                   0.25% w/v                                             Water                    to 100% by                                                                     volume                                                ______________________________________                                    

EXAMPLE 3

A (20:1) wettable powder was formed from:

    ______________________________________                                         Isoproturon              40% w/w                                               Diflufenican             2% w/w                                                Arylan S (sodium dodecyl benzene                                                                        2% w/w                                                sulphonate)                                                                    Darvan No. 2 (sodium lignosulphonate)                                                                   5% w/w                                                Aerosil (silicon dioxide of microfine                                                                   5% w/w                                                particle size)                                                                 Celite PF (synthetic magnesium silicate                                                                 46% w/w                                               carrier)                                                                       ______________________________________                                    

by mixing the ingredients and grinding the mixture in a hammer mill to give a wettable powder which may be diluted with water and applied at a rate of 6.25 kg per hectare in 200 liters of spray fluid per hectare to control a wide range of grass and broad-leaf weeds including Avena fatua and Galium aparine, by pre- or post-emergence application to a crop of winter wheat.

EXAMPLE 4

An (4:1) aqueous suspension concentrate was formed from:

    ______________________________________                                         Isoproturon              40% w/v                                               Diflufenican             10% w/v                                               Ethylan BCP (a nonylphenol-ethylene                                                                     2% w/v                                                oxide condensate containing 9 moles of                                         ethylene oxide per mole of phenol)                                             Antifoam FD (silicone emulsion                                                                          0.5% w/v                                              antifoaming agent)                                                             Pluronic L62 (an ethylene oxide/                                                                        2% w/v                                                propylene oxide block co-polymer)                                              Sopropon T36 (sodium salt of poly-                                                                      0.5% w/v                                              carboxylic acid)                                                               Attagel 50 (swelling attapulgite clay)                                                                  0.5% w/v                                              Water                    to 100% by                                                                     volume                                                ______________________________________                                    

by intimately mixing the ingredients and grinding in a ball-mill for 24 hours. The concentrate thus obtained may be dispersed in water and applied at an application rate of 2 liters per hectare pre- or post-emergence to a crop of barley to control a wide range of broad leaf weeds, including Galium aparine.

EXAMPLE 5

A (20:1) water dispersible granule form was formed by granulating the ingredients used in Example 3 with

water using a pan granulator into granules of 0.1-2 mm diameter. These granules can then be dispersed at a rate of 6.25 kg in 200 liters of water per hectare to control a wide range of grass and broad-leaf weeds by pre- or post-emergence application to a crop of winter wheat.

EXAMPLE 6

An (50:1) emulsifiable suspension concentrate was A formed from:

    ______________________________________                                         Isoproturon              50% w/v                                               Diflufenican             1% w/v                                                Ethylan TU (a nonyl phenol/ethylene                                                                     10% w/v                                               oxide condensate containing 10 moles                                           of ethylene oxide per mole of phenol)                                          Bentone 38 (an organic derivative of                                                                    0.5% w/v                                              special magnesium montmorillonite                                              thickener)                                                                     Aromasol H (an aromatic solvent                                                                         to 100% by                                            consisting predominantly of isomeric                                                                    volume                                                trimethylbenzenes)                                                             ______________________________________                                    

by intimately mixing the ingredients and grinding in a ball-mill for 24 hours. The emulsifiable suspension concentrate thus obtained may be diluted with water and applied at an application rate of 5 liters of emulsifiable suspension concentrate in 100 liters of spray fluid per hectare to control the growth of Alopecurus myosuroides, Viola arvensis and Veronica persica prior to the emergence of a crop of winter wheat.

EXAMPLE 7

A (1:2) tank mix of (a) the aqueous suspension concentrate of diflufenican (Example 2) and a 50% w/v commercial formulation of isoproturon (b) was prepared by adding 0.5 liters of (a) to 1 liter of (b) in 200 liters of water. The resulting spray fluid was applied to one hectare of wheat soon after emergence of the crop and weeds to control Galium aparine, Viola arvensis, Veronica hederifolia, Veronica persica, Stellaria media and Matricaria inodora.

EXAMPLE 8

A (1:70) tank mix of (a) the aqueous suspension concentrate of diflufenican (Example 2) and a 50% w/v commercial formulation of chlortoluron (b) was prepared by adding 0.1 liters of (a) to 7 liters of (b) in 200 liters of water. The resulting spray fluid was applied to one hectare of wheat soon after emergence of crop and weeds to control Avena fatua, Alopecurus myosuroides, Stellaria media, Matricaria inodora, Veronica persica and Viola arvensis.

EXAMPLE 9

A wettable powder was formed thus:

    ______________________________________                                         Neburon                 25% w/w                                                Nekal BX (sodium alkyl naphthalene                                                                     10% w/w                                                sulphonate                                                                     Sodium lignosulphonate  3% w/w                                                 Sopropon T36 (sodium polycarboxylate)                                                                  0.5% w/w                                               Silica filler           to 100% w/w                                            ______________________________________                                    

EXAMPLE 10

A (1.25:16) tank mix of (a) the aqueous suspension concentrate of diflufenican (Example 2) and a 50% w,w/ commercial formulation of isoproturon:neburon (1:1) (b) was prepared by adding 0.25 liters of (a) to 3.2 kg of (b) in 200 liters of water. The resulting spray fluid was applied to one hectare of wheat soon after emergence of crop and weeds to control Avena fatua, Alopecurus myosuroides, Stellaria media, Matricaria inodora, Veronica persica and Viola arvensis.

EXAMPLE 11

A (1:8.75) tank mix of (a) the aqueous suspension concentrate of diflufenican (Example 2) and a 70% w/w commercial formulation of methabenzthiazuron (b) was prepared by adding 0.4 liters of (a) to 2.5 kg of (b) in 200 liters of water. The resulting spray fluid was applied to one hectare of wheat soon after emergence of crop and weeds to control Avena fatua, Alopecurus myosuroides, Stellaria media, Matricaria inodora, Veronica persica and Viola arvensis.

In the mixed formulations in the Examples hereinbefore, the urea herbicide may be replaced by one other or a mixture of the urea herbicides. ##STR1## 

We claim:
 1. A method of controlling the growth of weeds at a locus which comprises applying to the locus an effective amount of a composition consisting essentially of (a) at least one urea herbicide of the general formula:

    R.sup.1 N(R.sup.2)CON(R.sup.3)R.sup.4                      I

whereinR² represents a hydrogen atom; R³ represents a group; R¹ represents a 3-chloro-4-methylphenyl or 4-isopropylphenyl group and R⁴ represents the methyl group, or R¹ represents a 3,4-dichlorophenyl group and R⁴ -represents a methyl, methoxy or butyl group, and; (b) diflufenican, which is N-(2,4-difluorophenyl)-2-(3-trifluoromethylphenoxy) nicotinamide,in which the application rate of the urea herbicide is in the range of about 150 g to about 4 kg per hectare and the application rate of diflufenican is in the range of about 25 g to about 750 g of diflufenican per hectare.
 2. A method according to claim 1 for the control of weeds in a crop in which the application rate of the urea herbicide is in the range of about 150 g to about 3500 g per hectare and the application rate of diflufenican is in the range of about 25 g to about 250 g of diflufenican per hectare.
 3. A method according to claim 1 for the control of weeds in a tree-growing area or plantation in which the application rate of the urea herbicide is between 1000 g and 4000 g per hectare and the application rate of diflufenican is between 100 g and 500 g of diflufenican per hectare.
 4. A method according to claim 1 for the control of weeds in a non-crop-growing area in which the application rate of the urea herbicide is between 2500 g and 4 kg per hectare and the application rate of difulfenican is between 200 g and 750 g of diflufenican per hectare.
 5. A method according to claim 1 for the control of annual broad-leafed and grass weeds in a cereal crop which comprises the pre- or post-emergence application of (a) a urea herbicide selected from chlortoluron, isoproturon, linuron and neburon or a mixture thereof and (b) diflufenican at application rates in a range of from about 500 to about 3500 g/ha and from about 50 to about 250 g/ha, respectively, in a ratio of 20:1 to 2:1 weight.
 6. A method according to claim 5 in which a mixture of urea herbicides is employed in a ratio of from 2:1 to 1:2 by weight.
 7. A method according to claim 1, 2, 3, 4 or 6 in which a mixture of urea herbicides is employed with said mixture being a mixture of isoproturon and neburon in a ratio in the range of 2:1 to 1:2 by weight.
 8. A method according to claim 7 in which the mixture ratio is 1:1 by weight.
 9. A method according to claim 5 in which the cereal crop is autumn-sown.
 10. A method according to claim 5 in which the urea herbicide is selected from chlorotoluron, isoproturon or neburon or a 2:1 to 1:2 mixture thereof, and in which the ratio of urea herbicide (a) to diflufenican (b) is 20:1 to 4:1 by weight.
 11. A herbicidal composition which consists essentially of an effective amount of(a) at least one urea herbicide of the general formula:

    R.sup.1 N(R.sup.2)CON(R.sup.3)R.sup.4                      I

whereinR² represents a hydrogen atom; R³ represents a methyl group; R¹ represents a 3-chloro-4-methylphenyl or 4-isopropylphenyl group and R⁴ represents the methyl group, or R¹ represents a 3,4-dichlorophenyl group and R⁴ represents a methyl, methoxy or butyl group, and; (b) diflufenican, in association with a herbicidally acceptable diluent or carrier and/or surface active agent in which the ratio of (a) to (b) ranges from 20:1 to 1:5 by weight.
 12. A herbicidal composition according to claim 11 in which the ratio of (a) to (b) ranges from 20:1 to 2:1 by weight.
 13. A herbicidal composition according to claim 11 in which the ratio of (a) to (b) ranges from 20:1 to 4:1 by weight.
 14. A herbicidal composition according to claim 11, 12 or 13 which consists essentially of from 0.05 to 90% by weight of diflufenican and urea herbicide. 